What exactly is PRaT???

@yoyoyaya "... The irony is that the ... LP12 of the mid eighties had dreadful micro timing stability due to the movement of the subchassis/armboard relative to the platter. Linn’s mantra was pitch and rhythm."

I lived in the UK before Linn, when speakers were regarded as the dominant factor in audio quality. Ivor’s argument was that distortions introduced at the start of the audio reproduction chain were also important.

His starting point was that any sloppiness between the cartridge and the record would be amplified by the cartridge. His engineering solution was to couple the cartridge to the platter as tightly as possible in the direction of the arm tube. The bearings that allowed the arm to track the groove, and the platter to rotate, had to have minimum play.

If different materials were used, which expanded at different rates, changes in temperature would open up gaps. So every mechanical connecting component was made of the same grade of stainless steel. The soft floating suspension allowed the entire platter, sub-chassis, arm, cartridge system to move as one, keeping the relationship between the cartridge and the record consistent.

The most obvious difference from competitive players was the response to transients, especially scratches in the record itself. Others exhibited lengthy mechanical ringing whereas scratches were much less obtrusive with Linn. Ivor the showman illustrated this through his casual handling of records in demonstrations, often throwing them around. Elsewhere I have tried to emphasize the importance of transients for our perception of PRaT.

My recollection is that specifications were notably absent from discussions of Naim products!  The same went for the specifications of Rolls Royce car engines, where the output was described as "sufficient".

Music reproduction systems produce sound waves that can be characterized by their amplitude, phase, and any added distortions.  Pace, rhythm and timing is something music has.  Unless you are using a turntable running at the wrong speed nothing in your system is going to change pace, rhythm, or timing.  The PRaT that audio writers prattle about is an illusion caused by dips and bumps in the frequency response of speakers or turntables.  Everything else has ruler flat frequency and phase response.  More or less PRaT in a solid state amplifier or DAC is purely imaginary.

@stuartk I would agree that all musical genres benefit to some level from better PRaT, but my perspective is that whether PRaT is a key element to understanding the music will vary by genre. Some musical genres like jazz have frequent quick interactions between different musicians. Better PRaT makes it easier in my experience to follow what's going on in the music. Orchestral music, as a vast generalization, tends to have interactions between the different instrumental sections that is of a nature that is not as quick and transient as those in jazz music.

@calvinandhobbes 

Orchestral music, as a vast generalization, tends to have interactions between the different instrumental sections that is of a nature that is not as quick and transient as those in jazz music.

Thanks for kindly pointing out what is probably obvious to many, here. I tend to favor smaller groups, which means I rarely listen to Big Band Jazz and never listen to orchestral music. My comments reflected my unfamiliarity/ignorance.

@rwortman

. . . The PRaT that audio writers prattle about is an illusion . . .

. . . and yet for some us, at least, the presentation of pace, rhythm and timing is discernibly different from one system to another.